Chidi Okwara asked “Can one run several operating systems in one computer?”
Not only can you do it, but it’s reasonably easy. Of course, all of the operating systems must be compatible with your hardware. Assuming your PC is less than five years old, it should be able to take Windows 7 and 8, along with almost any type of Linux. Just remember that you’ll need paid-for licenses for each version of Windows you install (not an issue with free Linux).
I’ll walk you through installing Windows 8 onto a Windows 7 PC. With minor differences, this should work with other operating systems, as well.